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arXiv:2609.07653

Microwave-Free $^{13}$C Hyperpolarization of Diamond Particles Enabled by Magic Angle Spinning and NV Centers

Rémi Blinder, Guzel Musabirova, Daehee Kim, Anshuman Nayak, Jason Twamley, Viateschlav N. Agafonov, Raiker Witter, Jörg Matysik, Fedor Jelezko

quant-phcond-mat.mtrl-sciSubmitted Sep 7, 2026• Announced Sep 8, 2026
v1 · Sep 7, 2026v2 · Oct 7, 2026
arXivHTMLPDF

Abstract

Nuclear hyperpolarization from optically pumped color centers in solids offers an alternative to conventional microwave-driven dynamic nuclear polarization (DNP). Diamond can host the nitrogen vacancy (NV) center, whose ground spin state can be readily polarized by light at room temperature, making diamond a candidate platform for nuclear hyperpolarization. We report $^{13}{\rm C}$ nuclear hyperpolarization in randomly oriented diamond particles with sizes ranging from 0.2 to 2 $μ$m, both at natural $^{13}{\rm C}$ abundance (1.1 %) and at 20 % isotopic enrichment, at magnetic fields of 7.1 T and 9.4 T. The protocol combines optical illumination with magic angle spinning (MAS) and does not require microwave irradiation. By investigating the nuclear polarization as a function of the MAS frequency between 0 and 6 kHz at the magnetic field of 7.1 T, we find maximum light-induced polarization enhancements of $280$-fold for the isotopically enriched sample and $411$-fold for the natural abundance sample. Under continuous illumination, steady-state absolute $^{13}{\rm C}$ polarization levels above 0.1 % are reached. A model involving optical pumping of NV centers and spin dynamics near level anticrossings (LACs) in three-spin clusters formed by NV, a substitutional nitrogen (P1) and $^{13}{\rm C}$ is used to describe these findings. The protocol strongly mitigates the effect of the anisotropy of the NV spin Hamiltonian, allowing more than $99.9\%$ of NV orientations to participate in the polarization transfer process. These results represent a first step toward transferring nuclear polarization from diamond particles to external nuclei, with potential applications in sensitive and high-resolution NMR at room temperature.

Comments
64 pages (38 main text + 26 SI), 26 figures (9 main text + 17 SI)

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Precision measurements based on optically detected nuclear magnetic resonance offer exquisite sensitivity to absolute shifts in spin transition frequencies, with potential applications in fundamental physics experiments and inertial sensing. We investigate 13C nuclear spins in diamond as a candidate system for solid-state implementations, which hold the promise for high-fidelity readout of large numbers of coherent nuclear spins in millitesla or lower magnetic fields. We demonstrate a technique that allows for both optical polarization and readout of large ensembles of ~10^{16} polarized nuclear spins. Our method takes advantage of state-selective Landau-Zener transitions under microwave frequency sweeping, which bidirectionally transfer spin polarization between Nitrogen-Vacancy (NV) electron spins and remote 13C nuclear spins. Using natural isotopic abundance diamonds with nitrogen densities of ~0.5-10 ppm, we perform optically-detected 13C Ramsey spectroscopy and realize a nuclear-spin-dependent fluorescence contrast exceeding 0.5% peak-to-peak. We observe nuclear spin dephasing times T2*~2 ms that only modestly improve with homonuclear dipolar decoupling, indicating that they are limited by the longitudinal spin relaxation of nearby NV electron spins. We study the magnetic field dependence of the optical readout and find comparable contrast and dephasing times for magnetic fields in the range 8-20 mT. Our method can be interpreted as a type of repetitive readout, where each NV center optically reads out the spin state of ~10^2 nuclei before nuclear spins depolarize.
We report a versatile method to polarize single nuclear spins in diamond, based on optical pumping of a single nitrogen-vacancy (NV) defect and mediated by a level anticrossing in its excited state. A nuclear-spin polarization higher than 98% is achieved at room temperature for the 15N nuclear spin associated with the NV center, corresponding to microK effective nuclear-spin temperature. We then show simultaneous initialization of two nuclear spins in the vicinity of a NV defect. Such robust control of nuclear-spin states is a key ingredient for further scaling up of nuclear-spin based quantum registers in diamond.
Abstract Hyperpolarization of nuclear spins is crucial for advancing nuclear magnetic resonance and quantum information technologies, as nuclear spins typically exhibit extremely low polarization at room temperature due to their small gyromagnetic ratios. A promising approach to achieving high nuclear spin polarization is transferring the polarization of electrons to nuclear spins. The nitrogen-vacancy (NV) center in diamond has emerged as a highly effective medium for this purpose, and various hyperpolarization protocols have been developed. Among these, the pulsed polarization (PulsePol) method has been extensively studied due to its robustness against static energy shifts of the electron spin. In this work, we present a novel polarization protocol and uncover a family of magic sequences for hyperpolarizing nuclear spins, with PulsePol emerging as a special case of our general approach. Notably, we demonstrate that some of these magic sequences exhibit significantly greater robustness compared to the PulsePol protocol in the presence of finite half π pulse duration of the protocol, Rabi and detuning errors. This enhanced robustness positions our protocol as a more suitable candidate for hyper-polarizing nuclear spins species with large gyromagnetic ratios and also ensures better compatibility with high-efficiency readout techniques at high magnetic fields. Additionally, the generality of our protocol allows for its direct application to other solid-state quantum systems beyond the NV center.
We report polarization of a dense nuclear-spin ensemble in diamond at room temperature. The method is based on the transfer of electron spin polarization of negatively charged nitrogen vacancy (NV) color centers to the nuclear spins via the excited-state level anti-crossing (ESLAC) of the center. We demonstrate polarization of 80% of the 14 N nuclear spins related to the NV centers, as well as that of 50% of the proximal 13 C nuclear spins. This work may enable polarization of the 13 C in bulk diamond, which is of interest to applications of nuclear magnetic resonance, quantum memories in hybrid quantum devices, and in sensing.
During the last decade, nitrogen-vacancy (NV) centers in diamond have gained a prominent role within the field of quantum technologies. These color defects inside the diamond lattice have been proved to be an extraordinary platform that assists in many of the current challenges that cutting-edge research is facing. The application of these novel tools exceeds the borders of quantum physics and reaches fields such as medicine, biology or chemistry. This thesis is focused on the development of novel theoretical schemes that intend to open new ways of understanding the NV centers as a quantum tool and sensor with direct applications. The manipulation of NV centers has become relatively easy in these last years. Moreover, via a proper control, the environment of an NV center may be overridden. In this thesis, we treat the NV center as a tool for enhancing the performance of nuclear magnetic resonance (NMR). Since the resolution of NMR is largely limited by the poor polarization of certain organic molecules, we here create and develop a theoretical frame that uses the NV center as a tool to transfer polarization toward organic samples in an efficient and controllable manner. In addition, this theoretical effort is supported by extensive numerical simulations and, moreover, all the predictions are confirmed by experimental evidence. Therefore, we demonstrate polarization transfer to external molecules at room-temperature paving the way for high-resolution NMR. Motivated by the success of the NV center as a polarization tool, we have further extended our analysis aiming to develop a phase transition sensor. In particular, we propose the NV center as a tool to assist current research on chemical reactions and molecular dynamics occurring at solid-liquid interfaces. These processes occur at a nanometric scale and thus, a nanometric sensor is desirable. In this context, the NV center is introduced as an ideal platform to investigate exotic phases of water when deposited onto diamond surface at room-temperature. In fact, recent studies predict that ultra-thin layers of water behave differently from bulk water due to interactions between water molecules and carbon atoms in the diamond surface. Through this thesis, we provide a theoretical and numerical work that predict how the NV center spin will behave in the presence of different phases of water, and hence, we reveal the NV center as a high-resolution sensor able to determine internal structures.
Negatively charged nitrogen-vacancy (NV−) centers in diamond have unique magneto-optical properties, such as high fluorescence, single-photon generation, millisecond-long coherence times, and the ability to initialize and read the spin state using purely optical means. This makes NV− centers a powerful sensing tool for a range of applications, including magnetometry, electrometry, and thermometry. Biocompatible NV-rich nanodiamonds find application in cellular microscopy, nanoscopy, and in vivo imaging. NV− centers can also detect electron spins, paramagnetic agents, and nuclear spins. Techniques have been developed to hyperpolarize 14N, 15N, and 13C nuclear spins, which could open up new perspectives in NMR and MRI. However, defects on the diamond surface, such as hydrogen, vacancies, and trapping states, can reduce the stability of NV− in favor of the neutral form (NV0), which lacks the same properties. Laser irradiation can also lead to charge-state switching and a reduction in the number of NV− centers. Efforts have been made to improve stability through diamond substrate doping, proper annealing and surface termination, laser irradiation, and electric or electrochemical tuning of the surface potential. This article discusses advances in the stabilization and enrichment of shallow NV− ensembles, describing strategies for improving the quality of diamond devices for sensing and spin-polarization transfer applications. Selected applications in the field of biosensing are discussed in more depth.